"""
Backup / DR target inventory snapshot.

Loads the latest committed, read-only Backup / DR target inventory. The
inventory is a planning artifact only; it never executes backups, restore,
offsite sync, credential marker writes, schedule changes, or destructive prune.
"""

from __future__ import annotations

import json
from pathlib import Path
from typing import Any

from src.services.snapshot_paths import default_evaluations_dir

_DEFAULT_EVALUATIONS_DIR = default_evaluations_dir(Path(__file__))
_SNAPSHOT_PATTERN = "backup_dr_target_inventory_*.json"
_SCHEMA_VERSION = "backup_dr_target_inventory_v1"


def load_latest_backup_dr_target_inventory(
    evaluations_dir: Path | None = None,
) -> dict[str, Any]:
    """Load the newest committed Backup / DR target inventory snapshot."""
    directory = evaluations_dir or _DEFAULT_EVALUATIONS_DIR
    candidates = sorted(directory.glob(_SNAPSHOT_PATTERN))
    if not candidates:
        raise FileNotFoundError(f"no Backup / DR target inventory snapshots found in {directory}")

    latest = candidates[-1]
    with latest.open(encoding="utf-8") as handle:
        payload = json.load(handle)

    if not isinstance(payload, dict):
        raise ValueError(f"{latest}: expected JSON object")
    _require_schema(payload, _SCHEMA_VERSION, str(latest))
    _require_read_only_boundaries(payload, str(latest))
    _require_operation_boundaries(payload, str(latest))
    _require_rollup_consistency(payload, str(latest))
    return payload


def _require_schema(payload: dict[str, Any], expected: str, label: str) -> None:
    actual = payload.get("schema_version")
    if actual != expected:
        raise ValueError(f"{label}: expected schema_version={expected}, got {actual!r}")


def _require_read_only_boundaries(payload: dict[str, Any], label: str) -> None:
    program_status = payload.get("program_status") or {}
    if program_status.get("read_only_mode") is not True:
        raise ValueError(f"{label}: program_status.read_only_mode must be true")

    boundaries = payload.get("approval_boundaries") or {}
    blocked_flags = {
        "sdk_installation_allowed",
        "paid_api_call_allowed",
        "shadow_or_canary_allowed",
        "production_routing_allowed",
        "destructive_operation_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: approval boundaries must remain false: {allowed}")


def _require_operation_boundaries(payload: dict[str, Any], label: str) -> None:
    boundaries = payload.get("operation_boundaries") or {}
    if boundaries.get("read_only_api_allowed") is not True:
        raise ValueError(f"{label}: read_only_api_allowed must be true")

    blocked_flags = {
        "backup_execution_allowed",
        "restore_execution_allowed",
        "offsite_sync_execution_allowed",
        "credential_marker_write_allowed",
        "schedule_change_allowed",
        "destructive_prune_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: operation boundaries must remain false: {allowed}")


def _require_rollup_consistency(payload: dict[str, Any], label: str) -> None:
    targets = payload.get("backup_targets") or []
    rollups = payload.get("rollups") or {}
    total = rollups.get("total_targets")
    if total != len(targets):
        raise ValueError(f"{label}: rollups.total_targets must equal backup_targets length")

    blocked_target_ids = set(rollups.get("blocked_target_ids") or [])
    actual_blocked = {target.get("target_id") for target in targets if target.get("status") == "blocked"}
    if blocked_target_ids != actual_blocked:
        raise ValueError(f"{label}: rollups.blocked_target_ids must match blocked targets")
